The present invention relates to venous access catheters. More specifically, the present invention relates to a multiple lumen catheter for improved resistance to cross lumen leakage at the hub and a method for making a catheter that provides improved resistance to cross lumen leakage at the hub. For example, a multiple lumen catheter according to the invention may be a peripherally inserted central catheter (PICC) or any other type of multiple lumen catheter known in the art.
A PICC is one type of catheter that may be used for the high pressure delivery of intravenous fluids. Previously, PICCs have been used for the low pressure delivery of intravenous fluids and medications. More recently it has become desirable to use a PICC for the administration of contrast agents during diagnostic Computer Tomography (CT) procedures and other radiographic procedures.
A PICC is a catheter that may be inserted in a peripheral location, such as the arm of a patient, with the tip of the PICC positioned above the heart in the superior vena cava. A PICC is intended for long term vascular access and may be designed to remain positioned within a patient for a period ranging from one week to a year. Of course, the period of time that a PICC remains within a patient is dependent on the medicinal regimen administered to the patient through the PICC. Because a PICC is designed for long term use in a patient, a PICC provides a convenient and comfortable means for the administration of medications and may be used in a wide variety of medical settings. For example, a PICC may be used with cancer patients undergoing long term therapy or during a high risk pregnancy where a constant infusion of medications and fluids may be required.
PICCs typically range from about 26 to about 16 gauge sizes. Fluid delivery rates range from about 26-30 cubic centimeters (cc) per hour for a 26 gauge PICC, to over a 1,000 cc per hour for a 16 gauge PICC. Typically, low pressure is used to administer fluids through PICCs at these rates. In comparison, CT procedures usually have an infusion rate of about 4 to 5 cc per second. Additionally, a thicker, more viscous fluid is used in CT procedures. Thus, the pressures involved in CT procedures are much higher.
The majority of currently available PICCs are only able to safely function at pressures less than 100 pounds per square inch (psi) and thus, are unable to meet the demands of high pressure applications where the pressures may reach and exceed 300 psi. Therefore, if a low pressure PICC has been used, a physician must access the patient's vein in another location using a short IV-type needle or catheter designed to withstand higher pressures. However, patients having an inserted PICC are often very ill and gaining access to a vein in another location may be difficult. More specifically, as veins are accessed over time, veins may become inaccessible through damage and scar tissue.
In addition to these low pressure PICCs, high pressure PICCs have been developed. When these currently available high pressure PICCs are used at high pressure, however the PICCs may develop cross-lumen leakage. This can be a serious problem because some medications that are simultaneously administered to a patient through a multiple lumen catheter may form a precipitate if mixed. The precipitate may partially or completely block the PICC, resulting in an unknown quantity of medication being administered to the patient. Alternatively, some medications if mixed prior to being dispersed through the blood stream may be extremely toxic and harmful to the patient.
Additionally, high pressure PICCs are expensive to manufacture. For example, currently available high pressure PICCs may use a titanium or steel hub that is inserted into an end of the catheter tubing. Plastic may then be molded over the metal hub and the end of the catheter tubing in an injection molding process.
The metal hub has several short comings. The metal hub must be machined to relatively tight tolerances and the metal itself may react to the medications being administered, which may limit its usefulness. Additionally, the metal hub complicates disposal of the catheter because it may need to be disposed of separately from the plastic portion of the catheter.
Another short coming of the prior art is that the catheter may still develop cross-lumen leakage at the interface between the metal hub and the catheter tubing. This is because of the radial stresses induced into each lumen of the catheter tubing by the fittings of the metal hub. In addition, low pressure PICCs made entirely of plastic may suffer from cross-lumen leakage at pressures as low as 40 psi.
Low pressure PICCS known in the art may be formed by cutting a multiple lumen catheter tube to size, inserting a mandrel into each lumen of the catheter, and molding a hub over the mandrels and the end of the multiple lumen catheter tube. Lastly, the mandrels are removed from the hub and extension legs attached to the hub to complete the catheter. A short coming of this type of catheter is that the multiple lumen catheter tube is cut flush so that the mandrels are positioned side by side in the end of the multiple lumen catheter tube which may stress and stretch the inner wall of the multiple lumen catheter tube. This stress and stretch of the inner wall of the multiple lumen catheter tube can result of cross-lumen leakage even under relatively low pressures, such as 40 psi.
Another shortcoming that can affect the performance of multiple lumen catheters is the formation of plastic flaps in the lumens of the catheter during the manufacturing process. As the hub is molded over the end of the multiple lumen catheter tube, the molding process may spread the mandrels allowing small fingers of plastic to flow into the lumens. Often these fingers of plastic have cooled enough that they fail to fully adhere to the multiple lumen catheter tube. Thus, these fingers of plastic may act as flaps that may potentially reduce the flow of liquids through that lumen of the catheter or may become dislodged and potentially flow into a patient.
Therefore, a need exists for a catheter that may be made entirely of plastic to facilitate the disposal and recycling of used catheters. A need exists for a hub that minimizes the radial stresses in the multiple lumen catheter tubing to increase the catheter's resistance to cross-lumen leakage. Additionally, a need exists for a method of manufacturing a catheter that resists the formation of flaps within the lumen of the catheter.